1. Field of the Invention
The invention relates generally to anchoring devices for well tools and, more particularly, but not by way of limitation, to anchoring devices especially adapted for securing various well tools within a string of well pipe or casing at preselected levels therein in such a manner that the proper installation of the anchoring device may be visually verified at the ground surface and the tools may be released and withdrawn from the well pipe or casing when desired.
2. Description of the Prior Art
The prior art includes various forms of anchoring and landing devices for use in installing tools in a pipe or casing string. A typical form of prior art anchoring and landing device includes a locator tool and and a latching collar or landing nipple placed in the pipe or casing string to establish a place to land an anchoring device. Such apparatus requires a set of latch elements variously called dogs or slips, on the anchoring device with a configuration which will correspond to the configuration of grooves or recesses formed in the landing nipple. When the locator tool is run into a well pipe, such as a tubing string, on a wire line, the tool will pass all collar recesses and other interruptions in the smooth bore of the tubing string, but when the tool comes to a recess in a landing nipple having a configuration matching that of the latch elements, the locator will project into the recess and anchor the tool at this point. Frequently several such tools must be landed in a tubing string and in order to accomplish this, sets of matching configurations for the latch elements and landing nipple recesses are required to selectively set the tools in the proper positions. Each landing nipple must have a configuration peculiar to the latches on the particular tool to be landed therein.
U.S. Pat. No. 3,130,788, to C. B. Cochran et al., discloses an anchoring device for well tools intended to provide improvements in economy and simplification over the apparatus described above. The Cochran apparatus employs a single set of latch elements and landing nipples having recesses of uniform configuration. This anchoring device is capable of being set in any one of a plurality of like landing nipples in a pipe string, and includes means for attaching the anchoring device to a wire line by which it could be run into the hole and for releasing the wire line from the anchoring device automatically when the tool is anchored.
It has been found, however, that apparatus such as that disclosed in the Cochran patent, adapted to be run and set on a wire line, are often unreliable due to improper setting of the anchoring device in the pipe string without the knowledge of the operator at the ground surface. Improper setting of such anchoring devices is extremely disadvantageous and hazardous under conditions where the anchoring device and tool mounted thereon must withstand relatively high pressures acting thereon from within the well such as in gas wells. Accordingly, it will be readily apparent that it is most advantageous to verify, at the ground surface, that an anchoring device for well tools has been properly latched and locked in a pipe or casing string before additional operations are conducted on a well in reliance on such device.